Methylmalonic Aciduria Type B Protein (MMAB)

MMAB encodes a protein that catalyzes the final step in the conversion of vitamin B₁₂ into adenosylcobalamin (AdoCbl), a vitamin B₁₂-containing coenzyme for methylmalonyl-CoA mutase. Mutations in the gene are the cause of vitamin B₁₂-dependent methylmalonic aciduria linked to the cblB complementation group.The deduced 250-amino acid protein has a calculated molecular mass of 27.3 kD. MMAB shares 88% sequence identity with mouse Mmu. MMAB gene consists of 9 exons extending over 18.87 kb. Exon 9 ends at 2 alternative polyadenylation sites, and the intron-exon junctions are conserved between man and mouse. MMAB has a predicted leader sequence and signal cleavage site consistent with localization to the mitochondria.